Crankshaft with floating crank throws



Oct. 11, 1966 N. B- KELL 3,277,743

CRANKSHAFT WITH FLOATING CRANK ZAROWS Filed April 20, 1964 2 Sheets-Sheet l INVENTOR.

Oct. 11, 1966 N. B. KELL 3, ,7 3

CRANKSHAFT WITH FLOATING CRANK THROWS Filed April 20, 1964 2 Sheds-Sheet 2 T INVENTOR.

ATTORNEY United States Patent i 3,277,743 CRANKSHAFT WITH FLOATING CRANK THROWS Nathaniel B. Kell, Indianapolis, Ind., assiguor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Apr. 20, 1964, Ser. No. 361,183 2 Claims. (Cl. 74-596) This invention relates to a crankshaft With floating crank throws that reduces the distance between the crank journal and the piston in a double acting pump or motor to that distance required for a single acting device.

The present conventional method of converting the reciprocating motion of pistons in a double acting pump or motor into rotary motion requires that the crank journal be a considerable distance from the piston. In addition to the piston rod, a crosshead and a connecting rod from the crosshead to the crank journal must be provided. Further, these components must be arranged linearly and space for their movement must be provided.

The following described invention will reduce the space required, in a double acting engine, to no more than that required for the crank motion of a single acting engine. The principle employed to facilitate the invention is: that a circle which rolls without slipping within another circle of twice the diameter of the first circle will cause any point on the first circle to describe a straight path which passes through the center of the larger circle.

The objects, features, and advantages of this invention will become obvious upon reference to the succeeding detailed description and the drawings illustrating the preferred embodiment thereof, wherein:

FIGURE 1 is a view, partially cut away, of an engine or pump mechanism having four cylinders and four pistons and the crank motion disclosed by the present invention;

FIGURE 2 is a view of the crankshaft mechanism as taken in the direction of arrows 22 in FIGURE 1;

FIGURE 3 is a view taken in the direction of arrows 3-3 in FIGURE 2;

FIGURE 4 is a schematic view of the conventional method of converting the reciprocating motion of double acting pistons into rotary motion;

FIGURE 5 is another embodiment of the crankshaft mechanism as shown in FIGURE 2 which uses a ring gear and toothed crank section instead of a crosshead to provide reaction means;

FIGURE 6 is a view taken in the direction of arrows 66 in FIGURE 5;

FIGURE 7 is a schematic view of the method of converting the reciprocating motion of pistons into rotary motion as disclosed by the present invention; and

FIGURE 8 is an enlarged schematic view of the crank elements of the subject invention.

The specific embodiments shown, when fitted with valve gear, ports, or fuel induction and exhaust means, could be used as a fiuid pump or motor, an internal combustion engine, or a steam engine. Either embodiment of the crankshaft illustrated could be applied to the piston and cylinder arrangement shown in FIGURE 1 or to other arrangements. The embodiment shown in FIGURES 1, 2 and 3, would be limited to arrangements having no less than two cylinders set at (or near) a 90 degree angle to each other. Therefore, limitation exists because the crosshead guides of each cylinder (or pair of cylinders) react against the angular thrust arising in the motion of the opposite piston rod (or rods). The embodiment shown in FIGURES 5 and 6 could be applied to cylinder arrangements of one or a number of cylinders, arranged at any desired angle to each other. "For angles other than 90 degrees or 180 degrees the crank journals require a like angular positioning (on a line passing through the 3,277,743 Patented Oct. 11, 1966 ice center or both the cylinder and overall crank throw circle). The crank journals 90 and 94 must always be angularly spaced apart (about the centers of journals 86 and 98) double the angular spacing of cylinders (about the centers of shafts and 52). This wider latitude in angular relation of cylinders is possible when the ring gear arrangement is used because the gears provide continuously efiicient thrust reaction characteristics, and no crosshead guides are used. In either version of the crank motion, side thrust cannot reach the piston and piston rods, except the crosshead portion of the piston rods in the first embodiment. In both embodiments of the crank motion, the gears and connecting shaft shown in FIGURE 2 are'necessary to stabilize the two end sections of the crankshaft, keeping them in identical rotational relation.

More specifically, the crank motion of the embodiment shown in FIGURES 1, 2 and 3 is as follows:

As seen in FIGURE 1, piston rods 10, 12, 14 and 16 reciprocate in and out of the cylinders '18, 20, 22 and 24, respectively. These cylinders are bounded and defined by an engine housing 26. Fixed to the ends of the four piston rods and maintaining a sliding relationship within the four cylinders, are four pistons 28, 30, 32 and 34. The four piston members are attached to their respective piston rods and fixed to them by means of nuts, such as those shown as 36 and 38 fixing piston 28 to piston rod 10. The four pistons maintain a sealed, sliding relationship with the four cylinders by means of piston rings 40 which may be of any type suitable for this application. The remaining details of the cylinders will be dependent upon their use, such as in a motor or in a pump.

The main subject of the invention, the crankshaft mechanism is housed Within a crankcase 42, which effectively seals the crankshaft mechanism from the effects of the ambient conditions. Each of the piston rods 16, 12, 14 and 16 enter the crankcase 42 thru cylindrical bores 44. The piston rods 10, 12, 14 and -16 maintain a sealed sliding relationship with the bores 44 of the crankcase 42 by means of seals 46. Such seals may be of any suitable type to maintain a tight sliding relationship between the piston rods and the crankcase. The cylinder housing 26 will be attached to the crankcase 42 by any suitable means such as the studs and nuts 48.

For a detailed study of the crankshaft mechanism we should turn our attention to FIGURE 2. The crankshaft is comprised at both ends by two axially aligned shafts 50 and 52. The shaft 52 is held within a bore 54 within the crankcase 42 .and is supported by a web 56, which is a structural portion of the crankcase 4-2. The other axially aligned shaft 50' extends through a bore' 58 in the crankcase 42 and is seated therein by crankshaft seal 60. It is to be noted that the portion of said axially aligned shaft 50 which extends outside of the crankcase 42 will be either the input or output shaft of the mechanism depending on whether the device is acting as a pump or as an engine. The shafts 50 and 52 must be connected through a suitable drive train so thatthey will have the same rotational speed. The specific embodiment of such a drive train as is used here includes gears 62 and 64 which transmit the motion of shaft 50 to a transmission shaft 66 which in turn transmits the motion through gears 68 and 70 to the other axially aligned shaft 52. As mentioned previously, the direction of the transmission of motion will depend upon the use to which the subject device is employed. The two axially aligned shafts 50 and 52 and the transmission shaft 66 rotate within suitable bearings such as those shown at 71.. The axia lly aligned shaft 50 also is supported by a web portion 72 of the crankcase 42. The inside ends of both shafts 50 and 52 have portions extending radially outward from the axes thereof. Formed within the portion 74 which extends outwardly from the axis of shaft 50 is a crank journal bore 76. The portion 78 extending radially outward from the axis of shaft 50in the opposite direction takes the shape of a counterweight as is best seen in FIGURE 3. Similarly, shaft 52 has a crank journal bore 80 in its upper radially extending portion 82 and its lower radially extending portion forms a counterweight 84. Thus, the radially extending portions of the axially aligned shafts 50 and 52 are identical.

The main portion of the crankshaft includes a crank journal 86 which is disposed within the bore 76 of shaft 50 and moves therewith while rotating therein. A crank throw member 88 connects the crank journal 86 to the crank throw journal 90, which is the crank pin for piston rods 10 and 12. The crank throw journal 90 is connected by a crank throw member 92 to a second crank throw journal 94, which is the pin member for piston rods 14 and 16 and which imparts the motion thereto (or receives motion therefrom in the case of an engine). The second crank throw journal 94 is connected by means of a crank throw 96 to the second crank throw journal 98 which is disposed within the bore 80 of the axially aligned shaft 52 and which moves therewith and rotates therein.

Thus, the crank member is rota-tably attached by means of the crank journals 86 and 98 to the pair of axially aligned shafts 50 and 52 and rotates therewith, and is further rotatably attached to the piston rods 10 and 12 by means of crank throw journal 90 and to piston rods 14 and 16 by means of crank throw journal 94 and these four crank journals are oonnected by means of the crank throws 88, 92 and 96.

It is seen in FIGURE 1 that the connected ends 100 and 102 of piston rods 10 and 12 form a bore 104 for the crank pin journal 90. These ends 100 and 102 of piston rods 10 and 12 may be fixed by any suitable means such as the stud and nut combination 106 shown in FIG- URE 1. Likewise, the connected ends 108 and 110 of piston rods 14 and 16 are fixed together by a stud and nut combination 112 to form a bore 114 for the crank pin journal 94. It is also seen that the connected ends 100 and 102 of piston rods 10 and12 form a crosshead 116 which slides between guides 118 and 120, which are part of the crankcase 42. Likewise, the connected end portions 108 and 110 of piston rods 14 and 16 form a crosshead 122 which slides between guides 124 and 126, which also are part of the crankcase 42.

Since the operation of the subject crankshaft is deemed to be novel, a complete description thereof is felt to be necessary. For purposes of description, we will assume that the shaft 50 rotates in the clockwise direction when viewed from the left end of FIGURE 2. When the subject crankshaft is used in a pump or compressor, the driving power is applied to the shaft 50 thereby rotating it in a clockwise direction. This rotational motion is transmitted through gears 62 and 64 to the trans-mission shaft 66 and then by means of gears 68 and 70 it is imparted to shaft -2. Thus shafts 50- and 52 are both rotating in a clockwise direction and at the same speed. It might be added that although we have assumed the direction of rotation to be clockwise, this direction of rotation is immaterial as the subject device will function equally well in either direction.

When crankshaft members 50 and 52 are rotating clockwise, crank journals 86 and 98 must move with the bores 76 and 80 into which they are fitted, and since these bores will move clockwise with their respective shafts 50 and 52, the crank journals 86 and 98 will rotate in the clockwise direction. However, since crank pin journals 90 and 94 can move only in the directions in which their bores in their respective erossheads 1-16 and 122 can move, it is apparent that they will be constrained to linear motion identical to the motion of the crossheads. In other words, the crank pin journal 90 will be con strained to move in the up and down direction as viewed 4 in FIGURE 2, and the crank pin journal 94 in the direction perpendicular to the plane of the drawings as viewed in FIGURE 2. It is to be noted here that the relationship between the piston rods 10 and 12 and that of piston rods 14 and 16 in the embodiment as shown by FIG- URES 1, 2 and 3, is degrees.

Thus, when crankshaft members 50 and 52 rotate clockwise, crank pin journal 90 can move only downward as viewed in FIGURE 2. Hence, since crank journal 86 will rotate clockwise and crank pin journal 90 will move downward, a counterclockwise motion will be imparted to the crank throw member 88. When the motion is started from the position illustrated, guide 120 is the react-ion member which guides crosshead 116 (FIGURE 1) and crank pin journal 90 in a straight line, and forces crank pin journal 94 to also move in straight line, but in a plane which is 90 degrees from the plane in which crank pin journal 90 moves. During the initial 90 degrees of rotation (90 degrees clockwise rotation of or-ank members 50 and '52 concurrently with 90 degrees counterclockwise rotation of crank throw member 88), the reaction point is transferred from crosshead guide 120 to crosshead guide 124 against which crosshead 122 formed by the connected ends 108 and 110 of piston rods 14 and 16 bears. During the next quarter of revolution, the reaction point is transferred from guide 124 to guide 118. In the third quarter revolution, the reaction point will transfer to guide 126, and in the final quarter of revolution, the reaction point again transfers to guide 120. It is the initial reaction point. From guide 118 the renot instantaneous but continues over each 90 degrees of crankshaft rotation and is completely on either guide only at the dead center posit-ions (90 degrees, 180 degrees, 270 degrees, and 360 degrees). In reverse rotation, guide 118 is the initial reaction point. From guide 118 the reaction point is transferred, in succession, to guides 124, 120, 126 and back to 118 in one revolution.

To simplify the preceding explanation, crankshaft members 50 and 52 rotate clockwise thereby causing crank journals 86 and 98 to rotate clockwise while crank throw member 88 rotates counterclockwise and causes crank pin journals 90 and 94 to move linearly thereby imparting axial reciprocation to each joined pair of piston rods. To secure such relative motion, it is mandatory that the radial spacing of crank pin journals 90 and 94 from crank journals 86 and 98 be equal to the radial spacing of crank journals 86 and 98 from the centers of the crank shaft members 50 and 52. A complete description of the aforementioned members will appear later in the specification. It should also be noted that when the cylinders are spaced at 90 degrees as illustrated, crank pin journals 90 and 94 must be 180 degrees apart. However, within reasonable limits, diiferent cylinder spacings can be employed if a suitable angular spacing of crank throws is made. For example, a 45 spacing of cylinders would require 90 spacing of journals 90 and 94.

An alternate embodiment of the invention employing the same inventive principle as the embodiment shown in FIGURES 1, 2 and 3 is shown in FIGURES 5 and 6. The component parts of the alternate embodiment are the same as the first embodiment except that there are no crosshead guides. Instead, a stationary ring gear 128 is the reaction member and a gear 130, integral with crank throw member 88, meshes with the stationary ring gear 128. Thus, when the crank shaft members 50 and 52 rotate clockwise, the gear 130 is forced to rotate counterclockwise, as it is fixed to crank throw member 88 which rotates counterclockwise within the stationary ring gear 128. This imparts the desired linear reciprocation to the crank pin journals 90 and 94, which in turn reciprocates the piston rods in the desired motion.

Thus when the gearing of the alternate embodiment is used instead of the crosshead and guides of the first embodiment, there are no restrictions on the cylinder spacing or on the number of cylinders. The angular spacing of the crank throws, of course, must correspond properly to the cylinder spacing as in the first embodiment. In this alternate embodiment, as in the first embodiment, the geometrical arrangement must be precise. The pitch diameter of gear 128 must be equal to the piston rod stroke and the pitch diameter of gear 130 must be equal to one half the pitch diameter of gear 128. It is to be further noted that the stationary gear 128 is fixed to a web portion 132 of the crankcase 42 by means of a plurality of studs 134. The radial spacing of the crank pin journals with respect to the crank journals and the shafts 50 and 52 must be the .same as their relationship in the first em bodiment.

It will now be shown that the subject device fulfills the objects previously mentioned and that it employs the principle set forth earlier in the specification, namely, that a circle which rolls without slipping within another circle of twice the diameter of the first circle will cause any point on the first circle to describe a straight path which passes through the center of the large circle. With respect to the first embodiment, as shown in FIGURES 1, 2 and 3, the radial spacing of the crank pin journals 90 and 94 fromt he crank journals 86 and 98 is equal to the radial spacing of the crank journals 86 and 98 from the axes of the shafts 50 and 52. This relationship is shown schematically in FIGURE 8, where the motion of one crank pin journal is depicted. The crank pin journal, the crank throw, and the crank journals are represented schematically and are given the same numbers as in FIGURE 2. It is seen in FIGURE 8 that as the crankshaft journal 86 rotates one-quarter of a revolution to the point designated at 86 the crank pin journal 90 will travel in a linear path to the position designated at 90. Thus, as the journal 86 travels one-quarter of a revolution (90 degrees), the crank pin journal 90 travels a linear distance designated as L. Further, as the crank journal travels from 86' to 86" the crank pin journal will travel from 90 to 90" thereby traveling a further linear distance L equal to that distance designated as L'.

Referring to FIGURE 4, a schematic diagram of the crank motion of a normal crankshaft and piston combination is depicted. It is seen that when the crank pin journal 150 travels one quarter of a revolution from point 160 to 160', the piston 164 travels a distance designated by A, from point 166 to 166. And further when the crank pin journal 150 travels the second one-quarter of a revolution the piston 164 travels the distance A from point 166' to 166". This motion is transferred by means of a connecting rod 162, a crosshead 168, and a piston rod 170. Thus, it is seen that the distances A and A' travelled by piston 164 during succeeding quarter revolutions are not equal due to the fact that the connecting rod 162 swings away from the axis of the piston rod or the first one quarter revolution and swings back during the second quarter revolution. It also should be noted that considerable linear space for the component parts is needed to accomplish this linear piston travel.

Now, in comparison, FIGURE 7 shows the crank motion and elements of the subject invention in the same scale as FIGURE 4. It is seen that the distance travelled by the piston 171 from 172 to 172 during the first quarter revolution is designated B, and that the distance B from 172 to 172" during the second quarter revolution is equal to the distance B. Hence it is apparent that the crank motion of the subject invention provides equal linear motion during each quarter revolution. It also can be seen that the same total linear travel as the FIG- URE 4 normal crankshaft can be obtained by the subject invention with a much smaller space needed for the component parts. The subject device also eliminates the need for a conventional crosshead and connecting rod.

Thus, the subject invention makes it possible to reduce the overall size of a double acting pump, motor or engine to a size which will not be greater than that of a single acting such device, and it provides a linear displacement which is the same in each quarter revolution.

Although the embodiments of this invention have been described for use ,in a device having only four cylinders, it is to be understood that it could be applied to such a device with any desirable number of cylinders, and that when using the second embodiment, the angular relationship between the cylinders can be varied to any desirable combinations.

Although but two embodiments of this invention have been described in detail, it should be obvious to those skilled in the art to which it pertains that they would have applications in many other embodiments and that many changes and modifications may be made thereto without departing from the scope of the invention.

I claim:

1. A reciprocating machine comprising:

a pair of axially aligned shafts, each of said shafts having radially extending portions forming a crank journal bore on one side of each of said shafts;

means to synchronize the rotation of said aligned shafts;

a crank throw member parallel with and connecting said pair of axially aligned shafts and having crank journals disposed within said crank journal bores of said axially aligned shafts, said crank member including two crank pin journals spaced from each other and from said crank journals by crank throws, said crank throws being sized so that the radial spacing of said two crank pin journals from said crank journals is equal to the radial spacing of said crank journals from the axis of said pair of axially aligned shafts;

a pair of connecting rods guided for linear reciprocating movement in quadrature to each other with respect to the said shafts, one connecting rod being journaled to each said crank pin journal;

and said crank throws being spaced at 180 around the axis of the crank journals.

2. A reciprocating machine comprising:

two axially aligned shafts, each of said shafts having radially extending portions forming a crank journal bore on one side of each of said shafts and a counterweight on the diametrically opposite side of each of said shafts;

means to synchronize the rotation of said aligned shafts including a connecting shaft and four gears;

a crank throw member parallel with and connecting said two axially aligned shafts and having crank journals disposed within said crank journal bores of said axially aligned shafts, said crank member including two crank pin journals spaced from each other and from said crank journals by crank throws, said crank throws being sized so that the radial spacing of said two crank pin journals from said crank journals is equal to the radial spacing of said crank journals from the axis of said two axially aligned shafts;

a pair of connecting rods guided for linear reciprocating movement in quadrature to each other with respect to the said shafts, one connecting rod being journaled to each said crank pin journal;

and said crank throws being spaced at 180 around the axis of the crank journals.

References Cited by the Examiner UNITED STATES PATENTS 1,136,121 4/1915 Gordon et al 123-55 1,732,424 10/1929 Young 74597 1,983,901 12/1934 Frampton 74597 2,650,543 9/1953 Pauget l03174 OTHER REFERENCES Product Engineering, September 1959, pp. 66-67.

FRED C. MATTERN, 111., Primary Examiner. BROUGHTON G. DURHAM, Examiner.

W. S. RATLIFF, JR., Assistant Examiner. 

1. A RECIPROCATING MACHINE COMPRISING: A PAIR OF AXIALLY ALIGNED SHAFTS, EACH OF SAID SHAFTS HAVING RADIALLY EXTENDING PORTIONS FORMING A CRANK JOURNAL BORE ON ONE SIDE OF EACH OF SAID SHAFTS; MEANS TO SYNCHRONIZE THE ROTATION OF SAID ALIGNED SHAFTS; A CRANK THROW MEMBER PARALLEL WITH AND CONNECTING SAID PAIR OF AXIALLY ALIGNED SHAFTS AND HAVING CRANK JOURNALS DISPOSED WITHIN SAID CRANK JOURNAL BORES OF SAID AXIALLY ALIGNED SHAFTS, SAID CRANK MEMBER INCLUDING TWO CRANK PIN JOURNALS SPACED FROM EACH OTHER AND FROM SAID CRANK JOURNALS BY CRANK THROWS, SAID CRANK THROWS BEING SIZED SO THAT THE RADIAL SPACING OF SAID TWO CRANK PIN JOURNALS FROM SAID CRANK JOURNALS IS EQUAL TO THE RADIAL SPACING OF SAID CRANK JOURNALS FROM THE AXIS OF SAID PAIR OF AXIALLY ALIGNED SHAFTS; A PAIR OF CONNECTING RODS GUIDED FOR LINEAR RECIPROCATING MOVEMENT IN QUADRATURE TO EACH OTHER WITH RESPECT TO THE SAID SHAFTS, ONE CONNECTING ROD BEING JOURNALED TO EACH SAID CRANK IN JOURNAL; AND SAID CRANK THROWS BEING SPACED AT 180* AROUND THE AXIS OF THE CRANK JOURNALS. 